The invention relates to an internal combustion (IC) piston engine with a positive displacement supercharger driven mechanically from the engine crankshaft for compression of the engine combustion air.
Superchargers so far used for the supercharging of IC piston engines are inefficient and expensive to manufacture so that they are so far not, in particular, suitable for small motor vehicle engines. Because of its satisfactory torque characteristic at low engines speeds, however, a mechanically driven displacement supercharger would seem inherently to be most suited for small private cars. The high costs of manufacture as noted, that more specially arise because it is hardly possible to make the air flow match requirements as based on the operating condition at a given time, and the high driving power that has to be delivered by the crankshaft, have so far greatly limited the use of mechanically driven superchargers for small vehicles.
The object of the present invention is to so design an IC engine of the sort noted at the outset herein that supercharger operation is worthwhile even in small vehicles.
In order to realize this object in the case of such an IC engine as noted at the outset, the piston displacement of one single supercharger chamber is made to suit the maximum air requirement of one engine cylinder to be supercharged, the stroke rate of the supercharging chamber or chambers of the supercharger is equal to the ignition frequency of the engine and the phase of piston motion of the supercharger bears a given relation to the piston motion of the engine in line with the desired supercharging effect.
The outcome of this is that it is then possible to supercharge with a relatively low power requirement, because the air from the supercharger may be displaced directly into the respective engine cylinder that it is to be filled so that no energy is needed for forcing out the air into a storage means or for forcing back the engine piston as the precompressed air flows into the engine cylinder.
In keeping with a useful development of the invention, and adjustable pressure controller, functioning as an air flow controller, is placed in the connection between the supercharger and the engine cylinder that is to be supercharged.
As part of particularly beneficial form of the invention a device for changing the phase relationship is placed in the driving connection between the engine crankshaft and the supercharger as an air flow controller.
A still further useful development of the invention which economizes in power is such that the piston displacement of one separate supercharger chamber is equivalent to the maximum amount of air desired in the engine cylinder to be filled less the amount of air drawn in by the engine piston and the phase relationship of the piston motion of the supercharger is so set in relation to the piston motion of the engine that the supercharger forces the maximum desired amount of extra air into the engine cylinder during the engine piston motion in the vicinity of bdc (bottom dead center).
It is furthermore possible as part of another development of the invention for the air amount control to be automatically set by the operational parameters of the overall system.
A more detailed account of the invention will now be given using the working examples thereof to be seen in the figures.